The long-term goal of this research is to develop a new technique that can monitor the release of identified neuropeptides. These transmitter molecules are found throughout the nervous system and regulate a wide variety of physiological processes. Changes in their patterns of release have been implicated in a spectrum of diseases including epilepsy and hypertension. However to fully appreciate the roles that these transmitters play in the physiological and pathological functioning of the nervous system requires that the factors controlling their release be identified. Due partially to the large number of different neuropeptides it is difficult to monitor the release of specific peptides on a physiological time scale. Amperometry is a technique that fulfills the important requirements of sensitivity and temporal resolution but can't be widely applied since many peptides are not oxidizable. We therefore propose to develop short oxidizable peptide tags that can be inserted into any neuropeptide prohormone. Following translation of the "tagged" prohormone these oxidizable peptides will act as unique molecular markers for a specific population of dense core granules. Secretion of the tag (and thus the other peptides on the same prohormone) can then be measured using amperometry. One advantage of this approach is that potentially it can be applied to any sequenced neuropeptide. To examine the utility of the technique we propose to test it in a variety of cell types and ultimately to develop a transgenic mouse that harbors the oxidizable tag in a restricted population of neuropeptide-containing dense core granules. The reagents that we propose to develop would allow the technique to be used by neuroscientists investigating a wide range of clinically relevant questions.